Citation
Overview
Urban areas can and do hold significant populations of birds, but we know surprisingly little about how these populations are connected with those present within the wider countryside. It has been suggested that the populations using these different habitats may be linked through seasonal movements, with individuals breeding in rural areas moving into urban sites during the winter months to exploit the supplementary food provided at garden feeding stations. However, little work has been done to test this hypothesis.
In more detail
This work was generously funded by a legacy gift from Jane Priest and grants from The Edward Cadbury Charitable Trust, The Marjorie Coote Animal Charity Trust and The John Spedan Lewis Foundation, for which we are incredibly grateful.
Abstract
ABSTRACT
Capsule: Blue Tits Cyanistes caeruleus and Great Tits Parus major wintering in rural areas tended to nmove further to breed the following breeding season and more frequently cross the urban–ruralboundary, than did those wintering in urban gardens.
Aims: To explore and quantify the movements of birds from winter to breeding season locations across the urban–rural ecotone at the boundary of a large urban area.
Methods: Birds were colour-ringed at rural and urban/suburban garden ringing sites during the winter. This was followed by breeding season surveys and resighting in the surrounding areas to quantify the movements of colour-ringed birds and changes in habitat selection between seasons.
Results: Blue Tits and Great Tits ringed in winter in rural areas tended to move further and selected more urbanized breeding territories the following spring than did urban/suburban garden-ringed conspecifics. This shows that the populations were connected across the urban–rural ecotone by the seasonal movements of individuals, but that net movement was from rural wintering areas to urban breeding habitat.
Conclusion: The results suggest that rural populations may not be subsidized by urban wintering birds and winter supplementary feeding, but that the resources in gardens within urban areas, perhaps spring/summer feeding and nestboxes, draw birds in to breed. Combined with independent evidence for lower breeding success in urban areas, this may show the operation of source-sink dynamics. The results suggest important implications for connections between populations, the conservation value of urban areas and potential for the spread of disease, but further work is required to extend evidence and inference to other regions and species. Nevertheless, the approach used here provides a scalable study model that can be applied in other contexts.
